The present invention concerns private telephone installations, in particular key systems and small time-division switches.
Installations of this kind serve a plurality of telephones and terminals and are conventionally connected by telephone subscriber lines to a local central office, usually forming part of a telephone network, to enable the telephones and terminals connected to the installation to communicate with telephones and terminals connected to the network but not to the installation.
Telephone installations of this kind are increasingly using time-division switching which entails encoding speech signals into digital form and which is well suited to transmission of voice or data on the same transmission media, according to changing user requirements.
Installations of this kind are managed by control units each based on at least one processor associated with a set of read-only and/or random access memories (ROM and/or RAM), the various units of the installation being connected with a specific architecture to the control unit managing them. Architectures designed for large telephone central offices are not necessarily suitable for smaller installations and are likely to lead to solutions which are expensive and which do not meet optimally the requirements of users.